The present invention relates to the field of testing and evaluation of objects according to variations in their internal characteristics.
Our copending application Ser. No. 117,565, now U.S. Pat. No. 3,768,645, teaches a procedure for inspecting objects such as citrus fruit for internal flaws and damage by the use of beams of X-rays which are used in such a manner that they simultaneously scan the interior portions of the fruit on opposite sides of the fruit, and in which the emergent X-ray beams are caused to generate electrical signals which are used in the fashion described in the aforesaid application Ser. No. 117,565, now U.S. Pat. No. 3,768,645, which is hereby included herein by reference, to effect a mechanical sorting of the fruit into a multiplicity of grades related to the extent of internal damage sensed by the X-ray scanning.
We have now found quite surprisingly that our inventive system as set forth in the aforesaid copending application can be made to operate satisfactorily if for the X-ray beams there are substituted optical beams, that is, beams of electromagnetic radiation having a wave length of from about 300 to about 4,000 nanometers. It is surprising that the system can be made to operate satisfactorily with scanning beams of the type just described, since even though they are to be sure electromagnetic radiation even as are X-rays, nevertheless X-rays pass through objects of the general nature of fruit with some absorption and relatively little scattering, whereas light beams within the optical range recited are subject not only to greater absorption than X-rays but to a relatively larger degree of scattering, leading to the emergence of the optical beam in a greatly diffused form. In spite of these facts, we have found that if a sufficiently sensitive photoresponsive sensor is utilized on the emergent side of the fruit, the beam still retains enough of a directional character so that by the use of a pair of collimating apertures responses can be obtained which effectively differentiate between the transmissibility characteristics of the two opposite sides of the fruit which are subjected to the scanning optical radiation.